LED filament and LED light bulb

ABSTRACT

An LED filament and an LED light bulb applying the same are provided. The LED filament includes a at least one LED section, wherein the at least one LED section comprises at least two LED chips electrically connected to each other through a first wire, and at least two conductive electrodes, wherein each of the at least two conductive electrodes is electrically connected to corresponding one of the at least one LED section; and a light conversion layer, covering the at least one LED section and a portion of each of the at least two conductive electrodes, a portion of the first wire is exposed outside the light conversion layer.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of Ser. No.16/894,913 filed on Jun. 8, 2020, which claims priority to ChinesePatent Applications No. 201910497661.2 filed on 2019 Jun. 10, which ishereby incorporated by reference in its entirety.

This application is a continuation-in-part application of U.S.application Ser. No. 16/748,070 filed on 2020 Jan. 21, which is acontinuation-in-part application of U.S. application Ser. No. 16/234,124filed on 2018 Dec. 27, which is a continuation-in-part application ofU.S. application Ser. No. 15/858,036 filed on 2017 Dec. 29.

The application Ser. No. 15/858,036 is a continuation-in-partapplication of U.S. application Ser. No. 15/499,143 filed on 2017 Apr.27.

The application Ser. No. 15/858,036 is a continuation-in-partapplication of U.S. application Ser. No. 15/723,297 filed on 2017 Oct.3.

The application Ser. No. 15/858,036 is a continuation-in-partapplication of U.S. application Ser. No. 29/619,287 filed on 2017 Sep.28.

The application Ser. No. 15/858,036 is a continuation-in-partapplication of U.S. application Ser. No. 29/627,379 filed on 2017 Nov.27.

The application Ser. No. 16/234,124 claims priority to Chinese PatentApplications No. 201510502630.3 filed on 2015 Aug. 17; No.201510966906.3 filed on 2015 Dec. 19; No. 201610041667.5 filed on 2016Jan. 22; No. 201610272153.0 filed on 2016 Apr. 27; No. 201610394610.3filed on 2016 Jun. 3; No. 201610586388.7 filed on 2016 Jul. 22; No.201610544049.2 filed on 2016 Jul. 7; No. 201610936171.4 filed on 2016Nov. 1; No. 201611108722.4 filed on 2016 Dec. 6; No. 201610281600.9filed on 2016 Apr. 29; No. 201710024877.8 filed on 2017 Jan. 13; No.201710079423.0 filed on 2017 Feb. 14; No. 201710138009.2 filed on 2017Mar. 9; No. 201710180574.5 filed on 2017 Mar. 23; No. 201710234618.8filed on 2017 Apr. 11; No. 201410510593.6 filed on 2014 Sep. 28; No.201510053077.X filed on 2015 Feb. 2; No. 201510316656.9 filed on 2015Jun. 10; No. 201510347410.8 filed on 2015 Jun. 19; No. 201510489363.0filed on 2015 Aug. 7; No. 201510555889.4 filed on 2015 Sep. 2; No.201710316641.1 filed on 2017 May 8; No. 201710839083.7 filed on 2017Sep. 18; No. 201710883625.0 filed on 2017 Sep. 26; No. 201730450712.8filed on 2017 Sep. 21; No. 201730453239.9 filed on 2017 Sep. 22; No.201730453237.X filed on 2017 Sep. 22; No. 201730537542.7 filed on 2017Nov. 3; No. 201730537544.6 filed on 2017 Nov. 3; No. 201730520672.Xfiled on 2017 Oct. 30; No. 201730517887.6 filed on 2017 Oct. 27; No.201730489929.X filed on 2017 Oct. 16; No. 201711434993.3 filed on 2017Dec. 26; No. 201711477767.3 filed on 2017 Dec. 29; No. 201810031786.1filed on 2018 Jan. 12; No. 201810065369.9 filed on 2018 Jan. 23; No.201810343825.1 filed on 2018 Apr. 17; No. 201810344630.9 filed on 2018Apr. 17; No. 201810501350.4 filed on 2018 May 23; No. 201810498980.0filed on 2018 May 23; No. 201810573314.9 filed on 2018 Jun. 6; No.201810836433.9 filed on 2018 Jul. 26; No. 201810943054.X filed on 2018Aug. 17; No. 201811005536.7 filed on 2018 Aug. 30; No. 201811005145.5filed on 2018 Aug. 30; No. 201811079889.1 filed on 2018 Sep. 17; No.201811277980.4 filed on 2018 Oct. 30; No. 201811285657.1 filed on 2018Oct. 31; No. 201811378173.1 filed on 2018 Nov. 19; No. 201811378189.2filed on 2018 Nov. 19; No. 201811549205.X filed on 2018 Dec. 18, No.201910060475.2 filed on 2019 Jan. 22; No. 201911057715.X filed on 2019Nov. 1; No. 201911234236.0 filed on 2019 Dec. 5; No. 201910497661.2filed on 2019 Jun. 10, each of which is hereby incorporated by referencein its entirety.

BACKGROUND Technical Field

The present invention relates to lighting fields, and more particularlyto an LED filament and an LED light bulb having the LED filament.

Related Art

LEDs have the advantages of environmental protection, energy saving,high efficiency, and long lifespan. Therefore, it has been generallyvalued in recent years and gradually replaced the position oftraditional lighting fixtures. However, the lighting of the traditionalLEDs is directional, and unlike traditional lighting fixtures, which canmake a wide-angle illumination. Therefore, applying LEDs to traditionallighting fixtures, depending on the types of the lighting fixtures,still has challenges.

In recent years, an LED filament that can make an LED light sourceresemble a traditional tungsten filament bulb and achieve 360°full-angle lighting has received increasing attention from the industry.This kind of LED filament is made by fixing a plurality of LED chips inseries on a narrow and slender glass substrate, and then wrapping theentire glass substrate with silica gel doped with a phosphor orphosphors, and then forming electrical connection. In addition, there isone kind of LED soft filament, which is similar to the structure of theabove-mentioned LED filament and is employed a flexible printed circuitsubstrate (hereinafter referred to FPC) instead of the glass substrateto enable the LED filament having a certain degree of bending. However,the soft filaments made by FPC have disadvantages. For example, sincethe FPC's thermal expansion coefficient is different from that of thesilicone-covered filament, long-term use will cause the LED chip todisplacement or even degumming; furthermore, the FPC may not beneficialto flexible adjustment of the process conditions and the like.

The applicant has previously disclosed a soft filament, for example, insome of the embodiments of Chinese Patent Publication No. CN106468405A,which provides a soft filament structure without a carrier substrate,and in the application, the traditional structure that needs the chip tobe mounted on the substrate before coating phosphor or packaging isreplaced by a flexible fluorescent package with a wavelength conversioneffect. However, some of the filament structures have challenges relatedto the stability of metal wiring between the chips while they are beingbent. If the arrangement of chips in the filament is dense, since thestress is too concentrated on a specific part of the filament upon thefilament is in a bent configuration, when adjacent LED chips areconnected by metal wiring, the metal wire connected to the LED chipswould be damaged or even broken easily. Therefore, some embodiments inthe application still have room for improvement in quality.

Most LED lights known to the inventor(s) use a combination of blue LEDchips and yellow phosphors to emit white light, but the emissionspectrum of LED lights in the red light region is weaker, and the colorrendering index is lower. Therefore, it is difficult for the traditionalLED lights to achieve a low color temperature. To increase the colorrendering index, generally a certain amount of green phosphor and redphosphor is added; however, the relative conversion rate of red phosphoris lower, leading to a reduction in the overall luminous flux of the LEDlights. That is, a decrease in light efficiency.

This application further optimizes the aforementioned applications tofit various kinds of processes and product requirements.

Furthermore, the LED filament is generally disposed inside the LED lightbulb, and in order to present the aesthetic appearance and to make theillumination of the LED filament more uniform and widespread, the LEDfilament is bent to have a plurality of curves. However, since the LEDchips are arranged in the LED filaments, and the LED chips arerelatively harder objects, the LED filaments can hardly be bent into adesired shape. Moreover, the LED filament is also prone to have cracksdue to stress concentration during bending.

SUMMARY

It is noted that the present disclosure includes one or more inventivesolutions currently claimed or not claimed, and in order to avoidconfusion between the illustration of these embodiments in thespecification, a number of possible inventive aspects herein may becollectively referred to “present/the invention.”

A number of embodiments are described herein with respect to “theinvention.” However, the word “the invention” is used merely to describecertain embodiments disclosed in this specification, whether or not inthe claims, is not a complete description of all possible embodiments.Some embodiments of various features or aspects described below as “theinvention” may be combined in various ways to form an LED light bulb ora portion thereof.

It is an object of the claimed invention to provide an LED filament,including:

a conductive section, including a conductor;

at least two LED sections connected to each other by the conductivesection, and each of the LED sections comprising at least two LED chipselectrically connected to each other through a wire;

two electrodes electrically connected to the LED section; and

a light conversion layer with a top layer and a base layer covering theat least two LED sections, the conductive section and the twoelectrodes, and a part of each of the two electrodes is exposedrespectively; wherein the LED filament is supplied with electric powerno more than 8 W, when the LED filament is lit, at least 4 lm of whitelight is emitted per millimeter of filament length of the LED filament.

In accordance with an embodiment with the present invention, the toplayer includes a phosphor composition that includes a first phosphor, asecond phosphor, a third phosphor, and a fourth phosphor, where theweight percentage of each phosphor in the phosphor composition is asfollow: the first phosphor is 5.45-5.55%, the second phosphor is 70-88%,the third phosphor is 0.6-7%, and the fourth phosphor is the rest amountof the phosphor.

In accordance with an embodiment with the present invention, the toplayer includes a glue where a weight ratio of the phosphor compositionto the glue in the top layer is from 0.2:1 to 0.3:1.

In accordance with an embodiment with the present invention, a peakwavelength of the first phosphor under an excitation of blue light is490-500 nm, and an full width at half maximum (FWHM) is 29-32 nm; whilea peak wavelength of the second phosphor under the excitation of bluelight is 520-540 nm, and an FWHM is 110-115 nm.

In accordance with an embodiment with the present invention, eachmillimeter of filament length includes at least two LED chips, and in a25° C. ambient environment, a temperature of the LED filament is nogreater than a junction temperature after the LED filament is lit for15,000 hours.

In accordance with an embodiment with the present invention, the LEDfilament includes a plurality of the LED sections, and each of the LEDsections includes a plurality of the LED chips, a shortest distancebetween two LED chips of the LED chips located respectively in twoadjacent LED sections is greater than a distance between two adjacentLED chips of the LED chips in the same LED section.

In accordance with an embodiment with the present invention, a length ofthe wire is shorter than a length of the conductor.

It is another object of the claimed invention to provide an LED lightbulb, comprising:

a lamp housing, filled with gas including nitrogen and oxygen, where theoxygen content is 1% to 5% of the volume of the lamp housing;

a bulb base connected to the lamp housing;

a stem connected to the bulb base and located in the lamp housing; and

a single LED filament, disposed in the lamp housing and the LED filamentcomprising:

a conductive section, comprising a conductor;

at least two LED sections connected to each other by the conductivesection, and each of the LED sections comprising at least two LED chipselectrically connected to each other through a wire;

two electrodes, electrically connected to the LED section; and

a light conversion layer with a top layer and a base layer, covering theat least two LED sections, the conductive section and the twoelectrodes, and a part of each of the two electrodes is exposedrespectively; wherein the LED filament is supplied with electric powerno more than 8 W, when the LED filament is lit, at least 4 lm of whitelight is emitted per millimeter of filament length;

a Cartesian coordinate system having a x-axis, a y-axis and a-z-axis isoriented for the LED light bulb, where the z-axis is parallel to thestem, wherein W1 is the diameter of the bulb base, W2 is the maximumdiameter of the lamp housing or the maximum horizontal distance betweenthe lamp housing in the Y-Z plane, and W3 is the maximum width of theLED filament in the y-axis direction on the Y-Z plane or the maximumwidth in the x-axis direction on the X-Z plane, where W1<W3<W2.

In accordance with an embodiment with the present invention, the LEDfilament has at least two first bending points and at least one secondbending point when the LED filament is bent. In accordance with anembodiment with the present invention, the at least two first bendingpoints and the at least one second bending point are arrangedalternately.

In accordance with an embodiment with the present invention, a height ofany one of the at least two first bending points on the Z-axis isgreater than a height of any one of the at least one second bendingpoint.

In accordance with an embodiment with the present invention, the LEDfilament has a plurality of the first bending points, distances betweenany of two adjacent first bending points of the first bending points onthe Y-axis are equal or distances between any of two adjacent firstbending points of the first bending points on the Z-axis are equal.

In accordance with an embodiment with the present invention, the LEDfilament has a plurality of the first bending points, a distance betweentwo adjacent first bending points of the first bending points on theY-axis has a maximum value D1 and a minimum value D2, or a distancebetween two adjacent first bending points of the first bending points onthe X-axis has the maximum value D1 and the minimum value D2, whereinthe range of D2 is from 0.5D1 to 0.9D1.

In accordance with an embodiment with the present invention, the LEDfilament include one conductor section and two LED sections, where abending point of each of the two LED sections and each of the twoelectrodes are located substantially on a circumference of a circletaking the conductor section as a center.

In accordance with an embodiment with the present invention, the LEDfilament includes a plurality of the LED sections, and each of the LEDsections includes a plurality of the LED chips, a shortest distancebetween two LED chips of the LED chips located respectively in twoadjacent LED sections is greater than a distance between two adjacentLED chips of the LED chips in the same LED section.

In accordance with an embodiment with the present invention, a length ofthe wire is shorter than a length of the conductor.

In accordance with an embodiment with the present invention, an impurityis attached to the inner wall of the lamp housing, where the averagethickness of the impurity deposited per square centimeter of an innerwall area of the lamp housing is 0.01 to 2 mm.

In accordance with an embodiment with the present invention, a spectraldistribution of the light bulb is between wavelength range of about 400nm to 800 nm, and three peak wavelengths P1, P2, P3 are appeared in thewavelength ranges corresponding to light emitted by the light bulb, thewavelength of the peak P1 is between 430 nm and 480 nm, the wavelengthof the peak P2 is between 580 nm and 620 nm, and the wavelength of thepeak P3 is between 680 nm and 750 nm, wherein a light intensity of thepeak P1 is less than that of the peak P2, and the light intensity of thepeak P2 is less than that of the peak P3.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the detaileddescription given herein below for illustration only, and thus notlimitative of the disclosure, wherein:

FIG. 1 illustrates a structural schematic view of an LED filamentaccording to an embodiment of the present invention;

FIGS. 2A to 2D illustrate a perspective view, a side view, another sideview, and a top view of an LED filament according to an embodiment ofthe present invention;

FIG. 3 illustrates a schematic emission spectrum of an LED filamentaccording to an embodiment of the present invention;

FIG. 4 illustrates a schematic emission spectrum of an LED filamentaccording to an embodiment of the present invention; and

FIG. 5 illustrates a schematic emission spectrum of an LED filamentaccording to an embodiment of the present invention.

FIGS. 6A to 6F are cross sectional views of various LED filaments inaccordance with the present invention;

FIG. 7A is a schematic structural view showing an embodiment of alayered structure of an LED filament in accordance with the presentinvention; and

FIG. 7B is a schematic structural view of an LED chip bonding wire of anembodiment in accordance with the present invention.

DETAILED DESCRIPTION

In order to make the abovementioned objects, features, and advantages ofthe present invention more comprehensible, specific embodiments of thepresent invention will be described in detail below with reference tothe accompanying drawings.

FIG. 1 is a schematic structural view of an embodiment of an LEDfilament of the present invention. As shown in FIG. 1 , the LED filament400 includes a light conversion layer 420, LED sections 402 and 404,electrodes 410 and 412, and a conductor section 430 located between theLED sections 402 and 404. The LED sections 402 and 404 include at leasttwo LED chips 442, and the LED chips 442 are electrically connected toeach other through a wire 440. In this embodiment, the conductor section430 includes a conductor 430 a connected to the LED sections 402 and404. The shortest distance between the two LED chips 442 locatedrespectively in two adjacent LED sections 402 and 404 is greater thanthe distance between the two adjacent LED chips 442 in the LED sections402/404. The length of the wire 440 is shorter than the length of theconductor 430 a. Therefore, when a bending portion is formed between thetwo LED sections 402 and 404, it can be ensured that the generatedstress will not cause the conductor section 430 to break. The lightconversion layer 420 is coated on at least two sides of the LED chip442/the electrodes 410 and 412. The light conversion layer 420 exposes apart of the electrodes 410 and 412. The light conversion layer 420 mayhave at least one top layer 420 a and one base layer 420 b serving as anupper layer and a lower layer of the LED filament, respectively. In thisembodiment, the top layer 420 a and the base layer 420 b are located ontwo sides of the LED chip 442/electrodes 410 and 412, respectively. Inone embodiment, if the LED filament is supplied with electric power nomore than 8 Watts (W), when the LED filament is lit, at least 4 lumen(lm) of white light is emitted per millimeter of filament length. In oneembodiment, each millimeter of filament length includes at least two LEDchips. In a 25° C. ambient environment, the temperature of the LEDfilament is no greater than the junction temperature after the LEDfilament is lit for 15,000 hours.

In one embodiment, a silicone-modified polyimide resin compositioncomposite film is served as a base layer 420 b of the LED filament. Inone embodiment, the amidation reaction is carried out under a nitrogenatmosphere or a vacuum defoaming method or both is employed in thesynthesis of the silicone-modified polyimide resin composition, so thatthe volume percentage of the cells in the composite film of thesilicone-modified polyimide resin composition is 5˜20%, preferably5˜10%. In one embodiment, the surface of the base layer 420 b may betreated with a silicone resin or a titanate coupling agent. After thesurface of the base layer 420 b is treated, the cells may contain thesilicone resin or the titanate coupling agent.

The phosphor composition that serves as a part of the top layer 420 aincludes a first phosphor, a second phosphor, a third phosphor, and afourth phosphor. The peak wavelength of the first phosphor under theexcitation of blue light is 490-500 nm, and the full width at halfmaximum (FWHM) is 29-32 nm. The peak wavelength of the second phosphorunder the excitation of blue light is 520-540 nm, and the FWHM is110-115 nm. The peak wavelength of the third phosphor under the bluelight excitation is 660-672 nm, and the FWHM is 15-18 nm. The peakwavelength of the fourth phosphor under the excitation of blue light is600-612 nm, and the FWHM is 72-75 nm; alternatively, the peak wavelengthof the fourth phosphor under the excitation of blue light is 620-628 nm,and the FWHM is 16-18 nm; or, the peak wavelength of the fourth phosphorunder the excitation of blue light is 640-650 nm, and the FWHM is 85-90nm. The center particle diameter (D50) of any one of the group of thefirst phosphor, the second phosphor, the third phosphor, and the fourthphosphor ranges from 15 μm to 20 μm. Preferably, in one embodiment, therange of the D50 of the second phosphor and the third phosphor is from15 to 16 μm, and the range of D50 of the first phosphor and the fourthphosphor is from 16 to 20 μm. When the blue light excites the phosphor,the different thickness of the top layer with consistent phosphorconcentration will affect the full width at half maximum of thephosphor. In this embodiment, the thickness of the top layer 420 a is80-100 μm. The weight percentage of each phosphor in the phosphorcomposition is as follow: the first phosphor is 5.45-5.55%, the secondphosphor is 70-88%, the third phosphor is 0.6-7%, and the fourthphosphor is the rest amount of the phosphor. The top layer is preparedat a certain ratio of phosphors to glue, phosphors with different peakwavelengths are selected, and the light performance is measured underthe condition using a blue LED chip with a peak wavelength of 451 nm anda FWHM of 16.3 nm and utilizing a current of 30 mA. The results of lightperformance of different phosphor compositions are shown in Table 1 asbelow:

TABLE 1 (part) Contents (%) First Second Third phosphor phosphorphosphor Fourth phosphor No. 495 nm 535 nm 670 nm 630 nm 652 nm 1 5.4972.55 0.83 21.13 2 5.49 72.55 2.54 15.45 3 5.51 85.83 5.04 3.62 4 5.5185.83 4.63 3.59 Total phosphor contents to Eff CCT No. glue ratio (%)(lm/w) Ra R9 (K) 1 27.4 103.5 94.7 93.0 2641 2 27.4 107.0 92.8 81.9 26833 27.6 102.0 97.0 91.5 2621 4 27.6 106.8 97.1 84.9 2670

It can be known from No. 1 to No. 4 of the top layers 420 a in Table 1that, the content of the third phosphor and the fourth phosphor in thephosphor composition will affect the light effect (Eff), the averagecolor rendering index (Ra), and the saturated red color (R9). It can beknown from compositions No. 1 and No. 2 that, when the content of thefourth phosphor with a peak wavelength of 670 nm increases, the Eff willincrease, but Ra and R9 will decrease. As can be seen from No. 3 and No.4 in Table 1, when the content of the fourth phosphor having a peakwavelength of 670 nm increases, the Eff will decrease, but Ra and R9will increase. Therefore, when the fourth phosphor with differentwavelength peaks is selected according to actual demands, the amounts ofthe third phosphor and the fourth phosphor may be adjusted to obtainbetter luminous performance.

Ratio Between Phosphors and Glue

Using the same phosphor, the ratio of the phosphor composition to theglue is adjusted and as shown in Table 2. As shown in Table 2, when theratio of the phosphor composition to the glue is different, the Eff, theRa, the R9, and the Correlated Color Temperature (CCT) will be differentas well. When the ratio of the phosphor composition to the glue is more,the Eff, the Ra, and the CCT will decrease, and the R9 decreases firstand then increases. Moreover, when utilizing the phosphor compositionaccompanied with a glue (such as silica gel) to form the top layer ofthe LED filament, since the specific weight of the phosphor compositionis greater than that of the silica gel, apparent precipitation of thephosphor will occur during the manufacturing process of the top layer,causing the white LED color temperature to drift. The more ratio of thephosphor composition to the glue, the more produced precipitation of thephosphor, resulting in a more severe color temperature drift. Therefore,the weight ratio of the phosphor composition to the glue in the toplayer is from 0.2:1 to 0.3:1, preferably, in one embodiment, from 0.25:1to 0.3:1. In one embodiment, a certain amount of hollow glass microbeadscan be added into the phosphor composition. When the phosphorprecipitates, the glass microbeads will float, and during the floatingprocess, the extent of backscattering/emission of light is reduced.Thus, the effect of light scattering resulting from the phosphorprecipitation will be offset, and therefore the color temperature driftphenomenon can be alleviated. In addition, since the microbeads absorbless visible light, the addition of the glass microbeads has littleimpact on the initial brightness of white light LEDs. The mass ratio ofthe glass microbeads to the phosphor composition is 1:5 to 1:15, and inone embodiment the weight ratio of the glass microbeads to the phosphorcomposition is preferably 1:10 to 1:15.

TABLE 2 (part) Contents (%) First Second Third Fourth phosphor phosphorphosphor phosphor No. 495 nm 500 nm 535 nm 670 nm 600 nm 1 4.01 7.1277.44 5.20 6.23 2 4.03 7.10 77.46 5.19 6.22 3 4.02 7.12 77.47 5.14 6.25Total phosphor contents to Eff CCT No. glue ratio (%) (lm/w) Ra R9 (K) 127.2 102.9 99.0 98.7 2718 2 35.2 91.9 98.6 98.5 2342 3 40.2 82.2 97.999.0 2128

In one embodiment, an LED filament is provided, and the provided LEDfilament is made of the aforementioned phosphor composition with a bluelight chip. The blue light chip has a wavelength peak of 450 to 500 nmand a full width at half maximum of 15 to 18 nm.

Please refer to FIGS. 2A and 2B to 2D. FIG. 2A shows a perspective viewof an LED bulb 40 h according to an embodiment of the present invention.FIGS. 2B to 2D show a side view, another side view, and a top view ofthe LED bulb 40 h in FIG. 2A, respectively. In this embodiment, as shownin FIGS. 2A to 2D, the LED bulb includes a lamp housing 12, a bulb base16 connected to the lamp housing 12, a stem 19, and a single LEDfilament 100 where the stem 19, and the single LED filament 100 are inthe lamp housing 12. The stem 19 includes a stem bottom and a stem top(or stand 19 a) opposite to the stem bottom. The stem bottom isconnected to the bulb base 16, and the stem top extends into theinterior of the lamp housing 12 (e.g., the stem top may be extended intoapproximately the center of the lamp housing 12). The LED filament 100includes a filament body and two filament electrodes 110 and 112. Thetwo filament electrodes 110 and 112 are located at opposite ends of thefilament body. The filament body is the part of the LED filament 100that excludes the filament electrodes 110 and 112.

During the manufacturing process of traditional bulbs, in order to avoida tungsten wire burning in the air thereby causing the oxidativefracture failure, a glass structure with a horn shape (hereinafter referto as “horn stem”) is designed to be disposed at the opening of theglass lamp housing and then the horn stem is sintered and sealed to theglass lamp housing. Then, a vacuum pump is connected to the lamp housingthrough the port of the horn stem to replace the air inside the lamphousing with nitrogen so as to suppress the combustion and oxidation ofthe tungsten wire inside the lamp housing. Eventually, the port of thehorn stem will be sintered and sealed. Therefore, the vacuum pump can beapplied to replace the air inside the lamp housing with full nitrogen orto configure a moderate ratio of nitrogen and helium inside the lamphousing through the stem to improve the thermal conductivity of the gasin the lamp housing and to remove the water mist in the air at the sametime. In one embodiment, the gas inside the lamp housing can also bereplaced with a moderate ratio of nitrogen and oxygen or a moderateratio of nitrogen and air. The oxygen or air content is 1% to 10%,preferably 1% to 5% of the volume of the lamp housing. When the baselayer contains saturated hydrocarbons, during the use of the LED bulbs,the saturated hydrocarbons will generate free radicals under the effectof light, heat, stress, etc. The generated free radicals or activatedmolecules will combine with oxygen to form peroxide radicals. Thus, thelamp housing filled with oxygen may increase thermal resistance andlight resistance of the base layer having saturated hydrocarbons.

During the manufacturing process of the LED bulb, in order to increasethe refractive index of the lamp housing 12 to the light emitted by theLED filament, some impurities, such as rosin, may be attached to theinner wall of the lamp housing 12. The lamp housing 12 can be vacuumdried to reduce the impurity content in the inner wall of the lamphousing 12 or in the gas filled in the lamp housing 12. After the lamphousing 12 is vacuum dried, the average thickness of the impuritydeposition per square centimeter of the inner wall area of the lamphousing 12 is 0.01 to 2 mm, and the thickness of the impurity ispreferably 0.01 to 0.5 mm. In one embodiment, the content of theimpurity per square centimeter of the inner wall area of the lamphousing 12 accounts for 1% to 30%, preferably 1% to 10% of the contentof the impurity on the inner wall of the entire lamp housing 12. Thecontent of the impurity can be adjusted, for example, by a method ofvacuum drying to the lamp housing 12. In another embodiment, a part ofimpurities may be left in the gas of the lamp housing 12, and thecontent of impurities in the gas is 0.1% to 20%, preferably 0.1 to 5%,of the volume of the lamp housing 12. The impurity content may beadjusted by the method of vacuum drying to the lamp housing 12. Becausea small amount of impurities is contained in the filling gas, the lightemitted by the LED filament is scattered or refracted by the impurities,and thus the light emitting angle may be increased, which is beneficialto improving the light emitting effect of the LED filament. Furthermore,since the impurity content in the filling gas is low, the heat transfereffect is increased, and the heat dissipation effect of the LED lightbulb is improved. Finally, by further reducing the impurity content inthe base layer 240 b (for example, the silicone-modified polyimide resincomposition), the strength of the base layer 240 b is increased, therebyeffectively increasing the service life of the LED filament.

A Cartesian coordinate system having an X-axis, a Y-axis and a Z-axis isoriented for the LED light bulb, where the Z-axis is parallel to thestem 19, and the LED filament 100 has at least two first bending pointand at least one second bending points when the LED filament is bent.The at least two first bending point and the at least one second bendingpoints are arranged alternately, and the height of any one of the atleast two first bending point on the Z-axis is greater than that of anyone of the at least one second bending points. In one embodiment, thedistances between any of two adjacent first bending points on the Y-axisor on the Z-axis are equal. Therefore, the appearance of the LEDfilament can be neat and beautiful. In an embodiment, the distancebetween the two adjacent first bending points on the Y-axis or on X-axishas a maximum value D1 and a minimum value D2, where the range of D2 isfrom 0.5D1 to 0.9D1, and the light flux distribution on each plane isrelatively consistent. Let (1) the diameter of the bulb base 16 be W1(shown in FIG. 2B), (2) the maximum diameter of the lamp housing 12 orthe maximum horizontal distance between the lamp housings 12 in the Y-Zplane be W2 (shown in FIG. 2B), and (3) the maximum width of the LEDfilament 100 in the Y-axis direction on the Y-Z plane (shown in FIG. 2B)or the maximum width in the X-axis direction on the X-Z plane be W3(shown in FIG. 2C). Specifically, FIGS. 2B and 2C are merelyillustrative, and the magnitude of W1, W2, and W3 is such that W3 isbetween W1 and W2, that is, W1<W3<W2, and is not a visual magnitude asshown in FIGS. 2B and 2C. When the LED filament is bent, the distancebetween adjacent first bending points and/or adjacent second bendingpoints in the Z-axis direction is wide, which is beneficial to improvingthe heat dissipation effect of the LED filament. In the manufacturingprocess of the LED bulb, the LED filament 100 can be folded into theinner space of the lamp housing 12 first, and then the filament 100 canbe manually or mechanically extended in the lamp housing 12 so that themaximum length of the filament 100 on the X-Z plane satisfies theabove-mentioned relationship.

As shown in FIG. 2A to FIG. 2D, in this embodiment, the LED filament 100has one conductor section 130 and two LED sections 102 and 104. The twoadjacent LED sections 102 and 104 are connected through the conductorsection 130. The bent portion of the LED filament 100 at the highestpoint has an arc shape. That is, the LED sections 102 and 104 show arcshapes respectively at the highest point of the LED filament 100. Theconductor section 130 shows an arc shape at the lower point of the LEDfilament as well. The LED filament 100 may be configured to have astructure where each bent conductor section 130 is followed by onesegment, and each LED sections 102,104 is formed into a respectivesection.

Moreover, since a flexible substrate (preferably made of asilicone-modified polyimide resin composition) is adopted by the LEDfilament 100, the LED sections 102 and 104 also have a certain degree ofbending ability. In this embodiment, the two LED sections 102 arerespectively bent to form an inverted U shape, and the conductor section130 is located between the two LED sections 102, and the degree ofbending of the conductor section 130 is the same as or greater than thatof the LED section 102. That is, the two LED sections 102 arerespectively bent at the higher point of the LED filament 100 to form aninverted U shape and have a bent radius R1. The conductor section 130 isbent at the lower point of the LED filament 100 and has a bent radiusR2, where R1 is greater than R2. The arrangement of the conductorsections 130 enables the LED filament 100 to achieve a bending with asmall turning radius in a limited space. In one embodiment, the bendingpoints of the LED section 102 and that of the LED section 104 are at thesame height in the Z direction. In addition, the height of the pole 19 acorresponds to the height of the conductor section 130. For example, thelowest portion of the conductor section 130 may be connected to the topof the pole 19 a, so that the overall shape of the LED filament 100 maynot be easily deformed. In different embodiments, the conductor sections130 may be connected to the pole 19 a by passing through a hole on thetop of the pole 19 a, or the conductor sections 130 may be connected tothe pole 19 a by being glued on the top of the pole 19 a, but is notlimited thereto. In one embodiment, the conductor section 130 and thepole 19 a may be connected by a conductive wire. For example, aconductive wire is extended from the top of the pole 19 a and connectedto the conductor section 130.

As shown in FIG. 2B, in this embodiment, in the Z direction, the heightof the conductor section 130 is higher than that of the two electrodes110 and 112. The two LED sections 102 may be seen as the two electrodes110 and 112 extending upward to the highest point respectively and thenbending down and further extending to connect to the conductor section130. As shown in FIG. 2C, in this embodiment, the outline of the LEDfilament 100 in the X-Z plane is similar to a V shape, that is, the twoLED sections 102 are extended obliquely upward and outward respectively,and are bent at the highest point then extended downwardly and inwardlyto the conductor section 130. As shown in FIG. 2D, in this embodiment,the outline of the LED filament 100 in the X-Y plane has an S shape. Asshown in FIG. 2B and FIG. 2D, in this embodiment, the conductor section130 is located between the electrodes 110 and 112. As shown in FIG. 2D,in this embodiment, in the X-Y plane, the bending point of the LEDsection 102, the bending point of the LED section 104, and theelectrodes 110, 112 are located substantially on a circumference of acircle taking the conductor section 130 as a center.

Please refer to FIG. 3 , which is a schematic emission spectrum of anLED light bulb according to an embodiment of the present invention. Inthis embodiment, the LED bulb lamp may be any LED bulb lamp disclosed inthe previous embodiments, and a single LED filament (which may be anyLED filament disclosed in the previous embodiments) is provided in theLED light bulb. By measuring the light emitted by the LED light bulbwith a spectrometer, a spectrum diagram as shown in FIG. 3 may beobtained. From the spectrum diagram, it can be seen that, the spectrumof the LED bulb lamp is mainly distributed between the wavelengths from400 nm to 800 nm, and three peaks P1, P2, P3 appear at three places inthis range. The peak P1 is about between 430 nm and 480 nm, the peak P2is about between 580 nm and 620 nm, and the peak P3 is about between 680nm and 750 nm. With regard to intensity, the intensity of the peak P1 issmaller than the intensity of the peak P2, and the intensity of the peakP2 is smaller than the intensity of the peak P3. As shown in FIG. 3 ,such a spectral distribution is close to the spectral distribution of atraditional incandescent filament lamp, and is also close to thespectral distribution of natural light. In an embodiment, a schematicemission spectrum of a single LED filament is shown in FIG. 4 . It canbe seen from this spectrum that, the spectrum of the LED bulb lamp ismainly distributed between the wave length from 400 nm to 800 nm. Thereare three peaks P1, P2, and P3 appear in this range. The peak P1 isbetween about 430 nm and 480 nm, the peak P2 is between about 480 nm and530 nm, and the peak P3 is between about 630 nm and 680 nm. Such aspectral distribution is close to the spectral distribution of atraditional incandescent filament lamp, and is also close to thespectral distribution of natural light.

Please refer to FIG. 5 . FIG. 5 is a light emission spectrum of an LEDlight bulb according to an embodiment of the present invention. As canbe seen from the figure, the spectrum distribution of the LED bulb lampbetween the wavelength of 400 nm to 800 nm has three peaks P1′, P2′, andP3′ similar to that shown in FIG. 4 . The difference is that theintensity of P1′ is greater than that of P1, and the full width at halfmaximum of P3′ is greater than that of P3. The LED bulb has an averagecolor rendering index Ra (R1-R8) greater than 95 and a saturated red(R9) greater than or equal to 90. The light efficiency (Eff) of the LEDfilament is greater than or equal to 100 lm/w.

The term “a filament” referred to in the present invention may be theaforementioned conductor section and the LED sections connected to eachother, or may be formed by LED sections only. The LED sections may havethe same and continuous light conversion layer (including the same andcontinuous top layer or bottom layer), and two conductive electrodeselectrically connected to the conductive bracket of the light bulb areonly provided at both ends. The structure that complies with the abovedescription is the single LED filament structure mentioned in thepresent invention.

As shown in FIG. 6A, in the present embodiment, the top layer 420 a ofthe LED sections 402, 404 has the largest diameter (or maximumthickness) in the radial direction of the LED filament and the diameterof the top layer 420 a is gradually reduced from the LED sections 402,404 to the conductive section 430, and a portion of the conductor 430 a(for example, the intermediate portion) is not covered by the top layer420 a. The base layer 420 b, whether in the LED sections 402, 404 or inthe conductive section 430, has substantially the same width, thicknessor diameter in the radial direction of the LED filament. In the presentembodiment the number of LED chips 442 in each of the LED sections 402,404 may be different. For example, some LED sections 402, 404 have onlyone LED chip 442, and some LED sections 402, 404 have two or more LEDchips 442. In addition to the number of the LED chip 442 designing ineach LED section 402, 402 is different, the types of the LED chip 442may also be different. It is acceptable as well that the number of theLED chip 442 designing in each LED section 402, 402 is consistent, andthe types of the LED chip 432 is different.

As shown in FIG. 6B, in the present embodiment, the top layer 420 a issubstantially uniform in width thickness or diameter in the radialdirection of the LED filament, whether in the LED sections 402, 404 orin the conductive section 430. A portion of the base layer 420 b hasbeen recessed or hollowed out corresponding to a portion of at least oneconductor 430 a, for example, the intermediate portion of the at leastone conductor 430 a is not covered by the base layer 420 b, and at leastone of the other conductors 430 a is completely covered by the baselayer 420 b.

As shown in FIG. 6C, in the present embodiment, the to layer 420 a issubstantially uniform in width, thickness or diameter in the radialdirection of the LED filament, whether in the LED sections 402, 404 orin the conductive section 430. A portion of the base layer 420 b hasbeen recessed or hollowed out corresponding to a portion of eachconductor 430 a, for example, the intermediate portion of the conductor430 a is not covered by the base layer 420 b.

As shown in FIG. 6D, in the present embodiment, the top layer 420 a ofthe LID sections 402, 404 has the largest diameter in the radialdirection of the LED filament, and the diameter of the top layer 420 ais gradually decreased from the LED sections 402, 404 to the conductivesection 430. Moreover, a portion of the conductor 430 a (for example,the middle portion) is not covered by the top layer 420 a, and a portionof the base layer 420 b is recessed or hollowed out such that a portionof the conductor 430 a (for example, the intermediate portion) is notcovered by the base layer 420 b. In other words, at least a portion ofthe conductor 430 a at the opposite sides thereof are not covered by thetop layer 420 a and the base layer 420 b, respectively.

As described above with respect to the embodiments of FIGS. 6B to 6D,when the base layer 420 b has a recession region or hollow regioncorresponding to a part of or all of the conductive sections 430, andthe recession region or the hollow region may be in the form of a slitor a groove. Therefore, the conductor 430 a is not completely exposedand the conductive section 430 can be provided with better bendability.

As shown in FIG. 6E, in the present embodiment, the conductor 430 a is,for example, a conductive metal sheet or a metal strip. The conductor430 a has a thickness Tc, and since the thickness of the LED chip 442 isthinner than the conductor 430 a, the thickness Tc of the conductor 430a is significantly greater than the thickness of the LED chip 442. Inaddition, with respect to the thickness of the LED chip 442, thethickness Tc of the conductor 430 a is closer to the thickness of thetop layer 420 a at the conductive section 430, for example.Tc=(0.7˜0.9)×D1, preferably Tc=(0.7˜0.8)×D1. In the meanwhile, thethickness of the top layer 420 a in the conductive section 430 can referto the diameter D1 in the radial direction of the aforementioned toplayer 420 a. Furthermore, in the present embodiment, the thickness ofthe top layer 420 a disposed on the LED sections 402, 404 and on theconductive section 430 is substantially consistent with the same. In themeanwhile, the thickness of the top layer 420 a in the LED sections 402,404 can be referred to the diameter D2 in the radial direction of theaforementioned top laver 420 a.

As shown in FIG. 6F, in the present embodiment, the thickness Tc of theconductor 430 a is also significantly greater than the thickness of theLED chip 442, however, the top layer 420 a of the LED sections 402, 404has the largest diameter in the radial direction of the LED filament.The diameter of the top laver 420 a is gradually reduced from the LEDsections 402, 404 to the conductive section 430, and a portion of theconductor 430 a, for example the intermediate portion, is not covered bythe top layer 420 a.

FIG. 7A is a schematic view showing an embodiment of a layered structureof the LED filament 400 of the present invention. The LED filament 400has a light conversion layer 420, two LED chip units 402, 404, twoconductive electrodes 410, 412, and a conductive section 430 forelectrically connecting adjacent two LED chip units 402, 404. Each ofthe LED chip units 402, 404 includes at least two LED chips 442 that areelectrically connected to each other by wires 440. In the presentembodiment, the conductive section 430 includes a conductor 430, and theconductive section 430 is electrically connected to the LED sections402, 404 through the wires 450. The shortest distance between the twoLED chips 442 located in the adjacent two LED chip units 402, 404 isgreater than the distance between adjacent two LED chips in the samechip unit 402/404. Moreover, the length of wire 440 is less than thelength of conductor 430 a. The light conversion layer 420 is disposed onthe LED chip 442 and at least two sides of the conductive electrodes410, 412. The light conversion layer 420 exposes a portion of theconductive electrodes 410, 412. The light conversion layer 420 maycomposed of at least one top layer 420 a and one base layer 420 b as theupper layer and the lower layer of the LED filament respectively. In thepresent embodiment, the LED chips 442 and the conductive electrodes 410,412 are sandwiched in between the top laver 420 a and the base laver 420b. When the wire bonding process of the face up chip is carried outalong the x direction, for example, the bonding wire and the bondingconductor are gold wires, the quality of the bonding wire is mainlydetermined by the stress at the five points A, B, C, D, and E as shownin FIG. 7B. The point A is the junction of the soldering pad 4401 andthe gold ball 4403, point B is the junction of the gold hall 4403 andthe gold wire 440, point C is between the two segments of the gold wire440, point D is the gold wire 440 and the two solder butted joints 4402,and the point E is between the two solder butted joints 4402 and thesurface of the chip 442. Because of point B is the first bending pointof the gold wire 440, and the gold wire 440 at the point D is thinner,thus gold wire 440 is frangible at points B and D. So that, for example,in the implementation of the structure of the LED filament 300 packageshowing in FIG. 7A, the top layer 420 a only needs to cover points B andD, and a portion of the gold wire 440 is exposed outside the lightconversion layer. If the one of the six faces of the LED chip 442farthest from the base layer 420 b is defined as the upper surface ofthe LED chip 442, the distance from the upper surface of the LED chip442 to the surface of the top laver 420 a is in a range of around 100 to200 μm.

The invention has been described above in terms of the embodiments, andit should be understood by those skilled in the art that the presentinvention is not intended to limit the scope of the invention. It shouldbe noted that variations and permutations (especially the embodimentsthat the LED filament provided in FIG. 1 combined to the LED light bulbprovided in FIG. 2 ) equivalent to those of the embodiments are intendedto be within the scope of the present invention. Therefore, the scope ofthe invention is defined by the scope of the appended claims.

What is claimed is:
 1. An LED filament, comprising: at least one LEDsection, wherein the at least one LED section comprises at least two LEDchips electrically connected to each other through a first wire; atleast two conductive electrodes, wherein each of the at least twoconductive electrodes is electrically connected to a corresponding oneof the at least one LED section; and a light conversion layer, coveringthe at least one LED section and a portion of each of the at least twoconductive electrodes; wherein a portion of the first wire is exposedoutside the light conversion layer; wherein the light conversion layercomprises a base layer, the base layer has an upper surface and a lowersurface, the upper surface comprises a first area and a second area, thesecond area comprises a cell, and a surface roughness of the first areais less than a surface roughness of the second area, wherein the lowersurface comprises a third area, and a surface roughness of the thirdarea is higher than the surface roughness of the first area, and whereinthe LED chips are positioned in the first area or the third area.
 2. TheLED filament according to claim 1, wherein the light conversion layercomprises a top layer, and the at least two LED chips and the at leasttwo conductive electrodes are between the top layer and the base layer.3. The LED filament according to claim 2, wherein the LED filamentcomprises at least two LED sections and a conductive section connectedto the at least two LED sections, the conductive section is attached toa surface of the base layer and contacts the top layer.
 4. The LEDfilament according to claim 2, wherein the top layer and the base layerare composed with different particles or particle densities.
 5. The LEDfilament according to claim 3, wherein the conductive section comprisesa conductor connected to an LED chip of the at least two LED chipsthrough a second wire, and a portion of the second wire is exposedoutside the light conversion layer.
 6. The LED filament according toclaim 5, wherein a diameter of the top layer is gradually decreased fromeach of the at least two LED sections to the conductive section, and aportion of the conductor is not covered by the top layer.
 7. The LEDfilament according to claim 6, wherein a portion of the conductor is notcovered by the base layer.
 8. The LED filament according to claim 5,wherein a portion of the conductor is not covered by the base layer. 9.The LED filament according to claim 7, wherein the portion of theconductor not covered by the top layer corresponds to the portion of theconductor not covered by the base layer.
 10. The LED filament accordingto claim 5, wherein the top layer has a largest diameter in a radialdirection of the LED filament, a diameter of the top layer is graduallydecreased from each of the at least two LED sections to the conductivesection, and a portion of the conductor is not covered by the top layer.11. The LED filament according to claim 1, wherein the LED filamentcomprises at least two LED sections, a shortest distance between two LEDchips in adjacent two LED sections of the at least two LED sections isgreater than a distance between two adjacent LED chips in each of the atleast two LED sections.
 12. The LED filament according to claim 1,wherein the lower surface further comprises a fourth area, and thesurface roughness of the third area is higher than a surface roughnessof the fourth area.
 13. An LED light bulb, comprising: a lamp housing; abulb base connected with the lamp housing; at least two conductivebrackets disposed in the lamp housing; a driving circuit disposed in thebulb base and electrically connected to the at least two conductivebrackets and the bulb base; and a light emitting part disposed in thelamp housing, wherein the light emitting part comprises: at least oneLED section, wherein the at least one LED section comprises at least twoLED chips electrically connected to each other through a wire; a lightconversion layer, covering the at least one LED section; and wherein aportion of the wire is exposed outside the light conversion layer;wherein the light conversion layer comprises a base layer, the baselayer has an upper surface and a lower surface, the upper surfacecomprises a first area and a second area, the second area comprises acell, and a surface roughness of the first area is less than a surfaceroughness of the second area, wherein the lower surface comprises athird area, and a surface roughness of the third area is higher than thesurface roughness of the first area, and wherein the LED chips arepositioned in the first area of the third area.
 14. The LED light bulbaccording to claim 13, wherein the light emitting part further comprisesat least two conductive electrodes, wherein each of the at least twoconductive electrodes is electrically connected to a corresponding oneof the at least one LED section.
 15. The LED light bulb according toclaim 14, wherein a portion of each of the at least two conductiveelectrodes is exposed outside the light conversion layer.
 16. The LEDlight bulb according to claim 14, wherein the light emitting partcomprises at least two LED sections and a conductive section connectedto the at least two LED sections, the conductive section is higher thanthe at least two conductive electrodes in a Z direction of the LED lightbulb, and the at least two LED sections are respectively shaped upwardfrom the at least two conductive electrodes to a highest point of thelight emitting part and then are bent down to connect with theconductive section.
 17. The LED light bulb according to claim 14,wherein the light emitting part comprises at least two LED sections anda conductive section connected to the at least two LED sections, each ofthe at least two LED sections respectively has a circular arc at ahighest point of the light emitting part, and the conductive section hasa circular arc at a low point of the light emitting part.
 18. The LEDlight bulb according to claim 14, wherein the light emitting partcomprises at least two LED sections and a conductive section connectedto the at least two LED sections, the at least two LED sections arerespectively bent at a high point of the light emitting part to beformed in a shape like an inverted deformed U letter and has a bendingradius value at R1, and the conductive section is bent at a low point ofthe light emitting part and has a bending radius value at R2, andwherein R1 is equal to or greater than R2.
 19. The LED light bulbaccording to claim 13, wherein the light emitting part has a contour ina shape like a V letter in an XZ plane of the LED light bulb.
 20. TheLED light bulb according to claim 13, wherein the light emitting parthas a contour in a shape like an S letter in an XY plane of the LEDlight bulb.
 21. An LED filament, comprising: at least one LED section,wherein the at least one LED section comprises at least two LED chipselectrically connected to each other through a first wire; at least twoconductive electrodes, wherein each of the at least two conductiveelectrodes is electrically connected to corresponding one of the atleast one LED section; and a light conversion layer, covering the LEDchips, a portion of each of the at least two conductive electrodes, anda portion of the first wire; wherein the light conversion layercomprises a base layer, the base layer has an upper surface and a lowersurface, the upper surface comprises a first area and a second area, thesecond area comprises a cell, and a surface roughness of the first areais less than a surface roughness of the second area, wherein the lowersurface comprises a third area, and a surface roughness of the thirdarea is higher than the surface roughness of the first area, and whereinthe LED chips are positioned in the first area or the third area. 22.The LED filament according to claim 21, wherein the LED filamentcomprises at least two LED sections, a shortest distance between two LEDchips in adjacent two LED sections of the at least two LED sections isgreater than a distance between two adjacent LED chips in each of the atleast two LED sections.
 23. The LED filament according to claim 21,wherein the lower surface further comprises a fourth area, and thesurface roughness of the third area is higher than a surface roughnessof the fourth area.
 24. The LED filament according to claim 21, whereinthe light conversion layer comprises a top layer, and the at least twoLED chips and the at least two conductive electrodes are between the toplayer and the base layer.
 25. The LED filament according to claim 24,wherein the top layer and the base layer are composed with differentparticles or particle densities.